High sensitivity detection of magnetic fields is critical to many applications including ordinance detection, geophysical mapping, navigation, and the detection of bio-magnetic fields associated with heart and brain activity. Conventional superconducting magnetometers based on superconducting quantum interference devices (SQUIDs) provide a high sensitivity for magnetic field detection but are bulky and require expensive cryogenic cooling. Atomic magnetometers, which are based on optical measurements of unpaired electron spin in an alkali metal vapor are being developed. These atomic magnetometers do not require cryogenic cooling and are capable of measuring the absolute magnetic field at high sensitivity (down to less than one femtoTesla).
The present invention provides an advance in the art of atomic magnetometers by providing an atomic magnetometer in which a pump light beam and a probe light beam are directed in substantially the same direction. This is useful to reduce lateral dimensions of the atomic magnetometer as compared to other types of atomic magnetometers. Additionally, the atomic magnetometers of the present invention provide a capability of sensing magnetic fields at an arbitrary angle orthogonal an optical path of the pump and probe light beams, whereas other types of atomic magnetometers in which the pump light beam is orthogonal to the probe light beam are limited to sensing a magnetic field in a single direction.
The present invention also utilizes two different wavelengths for the pump and probe light beams which allows the pump light beam to be blocked with an optical filter while allowing the probe light beam to be transmitted through the optical filter and detected to sense the magnetic field.
The atomic magnetometer of the present invention can be used with free-space or fiber optic delivery of the pump and probe light beams thereby allowing lasers used to generate the pump and probe light beams to be located at a distance from the atomic magnetometer. The use of fiber optic delivery of the pump and probe light beams is also advantageous to allow a plurality of atomic magnetometers to be supplied with pump and probe light beams from a single pair of lasers, with the pump and probe light beams being split and separately sent through optical fibers to each magnetometer.
These and other advantages of the present invention will become evident to those skilled in the art.